The present invention relates to a method for the preparation of a reinforced thermoplastic-resin (in particular, polyolefinic resin) composition and an apparatus for melting and kneading substances, which can suitably be used in the foregoing method. More particularly, the present invention relates to an improved technique which can ensure a strong affinity of a base resin for a reinforcing material incorporated into the resin and substantial solution of a problem concerning the so-called xe2x80x9cbridgingxe2x80x9d phenomenon occurred when a base resin, a reinforcing material and additives are melted and kneaded together, so that a melt-kneading apparatus can continuously be operated stably over a long period of time.
A molded product of a reinforced thermoplastic resin, which is produced from a reinforced thermoplastic resin composition comprising an inorganic reinforcing material such as a glass fiber reinforcing material or a inorganic flake filler and a thermoplastic resin (in particular, a polyolefin resin) shows a variety of advantages, by variously selecting the inorganic reinforcing materials. For instance, the molded product can be improved in mechanical properties such as the strength and rigidity thereof and any occurrence of warpage can effectively be prevented. Accordingly, such a reinforced thermoplastic resin composition has widely been used as a material for producing parts of cars such as motorcars, parts of aircraft and parts of shipping, as well as parts of various kinds of industrial machinery, parts and tools of industrial devices, construction materials and other materials.
If the foregoing inorganic reinforcing material and thermoplastic resin are introduced into a melt-kneading apparatus to thus melt and knead them, in the production of a reinforced resin-molded product, the reinforcing material is liable to cause classification at the supply port for the material due to an extreme increase in the viscosity of the molten resin and the incorporation of the inorganic reinforcing material into the base resin, and this in turn makes screws or the like of the melt-kneading apparatus susceptible to wear. In addition, there has been required further improvement in the interfacial affinity between a base resin and an inorganic reinforcing material and therefore, there still remains room for the improvement in, for instance, the durability of the molded product produced using the resulting reinforced resin composition (molten and kneaded product) and the strength and rigidity at a high temperature thereof.
Japanese Un-Examined Patent Publication (hereunder referred to as xe2x80x9cJ.P. KOKAIxe2x80x9d) No. Hei 4-25541 proposes, as a measure for the improvement of the interfacial affinity between a base resin and an inorganic reinforcing material, a reinforced polypropylene resin composition which comprises a modified polypropylene obtained by melting and kneading a mixture of an unmodified polypropylene, an unsaturated acid, an unsaturated silane compound and an organic peroxide, as a base resin; and glass fibers and powdery mica as inorganic reinforcing materials. It has been said that such a reinforced resin composition permits the improvement of the interfacial affinity between the base resin and the reinforcing materials incorporated into the resin and that the resin composition can be used as a material for a molded product having excellent durability.
However, if a reinforced resin composition is produced by introducing such a base resin and an inorganic reinforcing material into an extruder to thus melt and knead them in order to produce a molded product, a problem arises, such that there is still room for the improvement in the mechanical strength and rigidity under high temperature conditions, of the resulting molded product and the technique disclosed in the foregoing publication cannot eliminate, at all, the problems of classification and wear of screws, which are observed when the foregoing ingredients are admixed together.
On the other hand, J.P. KOKAI No. Hei 5-96532 proposes a method which utilizes an extruder provided with three supply ports for charging ingredients therein and which comprises the step of supplying, to the extruder, a mixture of polypropylene and an organic peroxide through the first supply port positioned on the most upstream side of the extruder; an inorganic flake filler through the second supply port positioned subsequent to the first supply port; and glass fibers through the third supply port positioned on the most downstream side of the extruder to thereby melt and knead these raw materials. It has been said that this preparation method permits the stable production of the aforementioned resin composition without accompanying any trouble such as classification at the supply ports and also permits the reduction of the wear of, for instance, the screws of the extruder.
In the method for producing such a reinforced resin composition, however, since further improvement of the interfacial affinity between the base resin and the inorganic reinforcing material are required, there is still room for the improvement in the durability of the molded product produced from the composition as well as the mechanical strength and rigidity, at a high temperature, of the molded product.
Taking into consideration the present state of the techniques for producing a reinforced resin compositions, the inventors of this invention have intensively investigated a method for melting and kneading raw materials in an extruder, which makes use of an extruder equipped with three supply ports and which comprises the step of supplying, to the extruder, a mixture of a polyolefin resin, an organic peroxide, an unsaturated acid and an organic silane compound through the first supply port positioned on the most upstream side of the extruder; an inorganic flake filler through the second supply port arranged subsequent to the first supply port; and a fibrous reinforcing material through the third supply port positioned on the most downstream side of the extruder. As a result, the inventors of this invention have succeeded in the preparation of a molded product from a reinforced polyolefin resin composition, excellent in the durability, substantially without accompanying any trouble such as the wear of the screws of the extruder, according to the foregoing method for producing the reinforced resin composition.
However, the method discussed above likewise suffers from a problem in that the xe2x80x9cbridgingxe2x80x9d phenomenon frequently occurs at the first supply port of the melt-kneading apparatus and consequently the apparatus cannot continuously be operated stably over a long period of time.
Accordingly, the present invention relates to an improved technique to solve the foregoing problems associated with the prior art and it is thus an object of the present invention to provide an improved method for producing a reinforced thermoplastic resin composition, which comprises melting and kneading raw materials for a reinforced resin-molded product containing a polyolefin resin, a fibrous reinforcing material and an inorganic flake filler as well as a melt-kneading apparatus suitably used in the preparation method.
More specifically, the object of the present invention is to provide a method and apparatus, which can ensure a high interfacial affinity between a base resin and a reinforcing material included in a reinforced thermoplastic resin composition and which permits the stable production of a reinforced thermoplastic resin composition capable of providing a reinforced resin-molded product excellent in, for instance, durability and mechanical strength and rigidity at a high temperature, without accompanying any problem such as the so-called xe2x80x9cbridgingxe2x80x9d phenomenon and wear of screws, over a long period of time.
The inventors of this invention have conducted various studies to develop a method for producing a reinforced thermoplastic resin composition using a polyolefin resin as a thermoplastic resin base material, substantially without accompanying the foregoing drawbacks and a production apparatus and have thus completed the present invention.
According to the present invention, there is provided a method for producing a reinforced thermoplastic resin composition, using a melt-kneading apparatus provided with a plurality of supply ports arranged in line with the direction along which a molten resin moves, which comprises the steps of:
supplying a polyolefin resin, a solid modifier and a solid radical generator through a first supply port positioned on the most upstream side of the extruder;
supplying an inorganic flake filler through a second supply port arranged at a position on the downstream side of the first supply port;
supplying a fibrous reinforcing material through a third supply port arranged at a position on the downstream side of the second supply port; and
supplying an unsaturated silane compound through a liquid-introducing port arranged at a position on the immediately downstream side of the first supply port and on the upstream side of the second supply port to thereby melt and kneaded the supplied components.
In the method for producing a reinforced thermoplastic resin composition according to the present invention, the inorganic flake filler is preferably powdery mica and the foregoing fibrous reinforcing material is preferably at least one member selected from glass fibers and carbon fibers.
The melt-kneading apparatus according to the present invention comprises:
a cylindrical barrel for melting a base resin introduced through the one side thereof, while moving the resin toward the other side thereof;
a means for melting and kneading the molten resin accommodated in the barrel;
first to third supply ports for the introduction of materials, arranged on the barrel in line with the direction along which the molten resin moves; and
a liquid-introduction port arranged at a position on the immediately downstream side of the first supply port and on the upstream side of the second supply port.
In the melt-kneading apparatus according to the present invention, the melt-kneading means thereof may be an extruder provided with a screw and in this case, a seal ring region is preferably arranged at a position between the first and second supply ports of the screw.
In the melt-kneading apparatus according to the present invention, it is desirable that the liquid-introduction port be arranged at a position on the downstream side of the first supply port and within a section wherein the ratio (L/D) of the length to the diameter of the barrel satisfies the following formula: L/Dxe2x89xa62 and that the section extending from the liquid-introduction port to the second supply port satisfy the relation: L/Dxe2x89xa78.
In addition, according to a preferred embodiment of the melt-kneading apparatus of the present invention, the apparatus has such a structure that the liquid-introduction port is a through hole formed through the barrel at a position in the vicinity of the first supply port and, to the through hole, a means for feeding a substance under pressure is fitted, said means feeding the liquid unsaturated silane compound to the barrel.